Techniques for surface preparation during additive fabrication and related systems and methods

ABSTRACT

According to some aspects, an additive fabrication device is provided configured to form layers of material on a build platform, each layer of material being formed so as to contact a container in addition to the build platform and/or a previously formed layer of material. The additive fabrication device may comprise a container and a wiper, wherein the wiper comprises a wiper arm and a wiper blade coupled to said wiper arm using a pivoting coupling.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit as a continuation under 35U.S.C. § 120 of U.S. patent application Ser. No. 16/279,820, filed Feb.19, 2019, which claims the benefit as a continuation under 35 U.S.C. §120 of U.S. patent application Ser. No. 15/248,295 (now U.S. Pat. No.10,207,453), filed Aug. 26, 2016, which claims the benefit under 35U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/211,321,filed Aug. 28, 2015, each of which is hereby incorporated by referencein its entirety.

BACKGROUND

Additive fabrication, e.g., 3-dimensional (3D) printing, providestechniques for fabricating objects, typically by causing portions of abuilding material to solidify at specific locations. Additivefabrication techniques may include stereolithography, selective or fuseddeposition modeling, direct composite manufacturing, laminated objectmanufacturing, selective phase area deposition, multi-phase jetsolidification, ballistic particle manufacturing, particle deposition,laser sintering or combinations thereof. Many additive fabricationtechniques build parts by forming successive layers, which are typicallycross-sections of the desired object. Typically each layer is formedsuch that it adheres to either a previously formed layer or a substrateupon which the object is built.

In one approach to additive fabrication, known as stereolithography,solid objects are created by successively forming thin layers of acurable polymer resin, typically first onto a substrate and then one ontop of another. Exposure to actinic radiation cures a thin layer ofliquid resin, which causes it to harden and adhere to previously curedlayers or to the bottom surface of the build platform.

SUMMARY

The present application relates generally to systems and methods forcleaning and wiping surfaces within an additive fabrication (e.g.,3-dimensional printing) device.

According to some aspects, an additive fabrication device is providedconfigured to form layers of material on a build platform, each layer ofmaterial being formed so as to contact a container in addition to thebuild platform and/or a previously formed layer of material. Theadditive fabrication device may comprise a container and a wiper,wherein the wiper comprises a wiper arm and a wiper blade coupled tosaid wiper arm using a pivoting coupling.

According to some aspects, a wiper is provided configured to be usedwithin an additive fabrication device. The wiper may comprise a supportstructure configured to be attached to one or more components of theadditive fabrication device, a wiper arm coupled to the supportstructure having a long axis aligned in a first direction, and a wiperblade coupled to said wiper arm using a pivoting coupling. The wiperblade may have a long axis aligned in the first direction and maycomprise a first surface and a second surface aligned perpendicularly tothe first direction, the second surface being longer than the firstsurface. The wiper blade may further comprise a void space locatedbetween said first and second surfaces and configured to hold liquid.

The foregoing is a non-limiting summary of the invention, which isdefined by the attached claims.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments will be described with reference to thefollowing figures. It should be appreciated that the figures are notnecessarily drawn to scale. In the drawings, each identical or nearlyidentical component that is illustrated in various figures isrepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing.

FIGS. 1A-1B depict an illustrative additive fabrication system,according to some embodiments;

FIG. 1C depicts resin pieces that are not adhered to a part afterseparation of the part from the container, during additive fabrication,according to some embodiments;

FIGS. 2A-2B illustrate two views of an illustrative wiper, according tosome embodiments;

FIGS. 3A-3B are schematics showing two different views of anillustrative stereolithographic printer that includes a wiper, accordingto some embodiments;

FIG. 4 is a schematic of an illustrative wiper, according to someembodiments;

FIG. 5 depicts a cross sectional view of an illustrative wiper bladealong the horizontal axis of motion, according to some embodiments;

FIGS. 6A-6D depict various stages during operation of a wiper, accordingto some embodiments;

FIGS. 7A-7B depict use of an illustrative wiper to dislodge material notadhered to a part being fabricated, according to some embodiments; and

FIG. 8 depicts transport of dislodged material into a recessed portionof a container, according to some embodiments.

DETAILED DESCRIPTION

As discussed above, some additive fabrication techniques form solidobjects by solidifying (also referred to herein as “curing”) a liquid,such as a photopolymer resin. Sometimes when using such techniques, aregion of liquid may be cured to a solid or partially solid state butfail to adhere to the object being fabricated. This may occur for avariety of reasons, such as an incompletely performed curing operationand/or adhesion of cured or partially cured material to a surface otherthan the object being fabricated (e.g., to a container). When thisoccurs, the cured or partially cured material may subsequently interferewith the successful forming of a remainder of the object, such as byadhering to an undesired location on the object and/or by inhibiting thecorrect formation of subsequent material (e.g., by blocking the path ofa radiation source, by mechanically sticking to the object and therebyintroducing undesirable forces, etc.).

To depict an example of cured and/or partially cured material failing toadhere to an object being fabricated, an illustrative additivefabrication system is depicted in FIGS. 1A-1C. Illustrativestereolithographic printer 100 forms a part in a downward facingdirection on a build platform such that layers of the part are formed incontact with a surface of a container in addition to a previously curedlayer or the build platform. In the example of FIGS. 1A-1C,stereolithographic printer 100 comprises build platform 104, container106 and liquid resin 110. A downward facing build platform 104 opposesthe floor of container 106, which contains a photopolymer resin 110.FIG. 1A represents a configuration of stereolithographic printer 100prior to formation of any layers of a part on build platform 104.

As shown in FIG. 1B, a part 112 may be formed layerwise, with theinitial layer attached to the build platform 104. In FIG. 1B, the layersof the part 112 are each formed from the same material but are shown inalternating colors merely to visually distinguish them in this example.The container's base surface may be transparent to actinic radiation,such that radiation can be targeted at portions of the thin layer ofliquid photocurable resin resting on the base surface of the container.Exposure to actinic radiation cures a thin layer of the liquid resin,which causes it to harden. The layer 114 is at least partially incontact with both a previously formed layer and the surface of thecontainer 106 when it is formed. The top side of the cured resin layertypically bonds to either the bottom surface of the build platform 104or with the previously cured resin layer in addition to the transparentfloor of the container. In order to form additional layers of the partsubsequent to the formation of layer 114, any bonding that occursbetween the transparent floor of the container and the layer must bebroken. For example, one or more portions of the surface (or the entiresurface) of layer 114 may adhere to the container such that the adhesionmust be removed prior to formation of a subsequent layer.

Following the curing process, a separation process is typicallyconducted so as to break any bonds that may have been produced betweenthe cured material of layer 114 and the bottom of container 106. Varioustechniques may be employed to separate the layers, include rotationand/or sliding the container relative to the build platform. As oneexample, build platform 104 may be moved away from the container toreposition the build platform for the formation of a new layer and/or toimpose separation forces upon any bonds between cured and/or partiallycured material and the bottom of the container. In some implementations,the container 106 may be mounted onto a support base such that thecontainer can be moved along a horizontal axis of motion (left or rightin FIG. 1B) to introduce additional separation forces.

As discussed above, in some cases partially and/or fully cured regionsof the photopolymer resin may not adhere to the object being fabricated.For instance, when a layer of resin is cured in contact with apreviously formed solid layer (e.g., layer 114) and the bottom ofcontainer 106, and then subsequently separated from the container, someresin may nonetheless still adhere to the bottom of the container afterthe separation. This resin may, for instance, be a thin layer orpartially and/or fully cured resin that is at least somewhat adhered tothe container, and/or may include pieces of partially and/or fully curedresin that have adhered to the container.

FIG. 1C illustrates two pieces of partially cured and/or fully curedresin 125 and 126 that are not adhered to the part 112 after separationof the part from the container. For clarity, the pieces 125 and 126 areshown as having a larger size than might typically be expected withinthe scale of the figure. In general, such resin pieces may have a sizeequal to or less than the thickness of a layer produced by the additivefabrication device, though may sometimes be of a larger size. Forinstance, an additive fabrication device that forms layers having athickness of 50 μm (0.05 mm) may, in some cases, produce partially curedand/or fully cured resin pieces having a dimension between 0 and 50 μm.Irrespective of their size, the partially cured and/or fully cured resinpieces may be partially or fully adhered to the container 106, or maynot be adhered to the container at all and may be “floating” in theresin 110. These resin pieces may negatively impact the formation ofsubsequent layers of the part 112, such as by adhering to one or more ofthe subsequent layers or otherwise. In extreme cases, such resin piecescan block a subsequent layer from being formed by impinging on theincident actinic radiation, thereby leading to a missing portion in thepart once fabricated.

The inventors have recognized and appreciated that a moveable wiperpositioned to move over the surface of a container of an additivefabrication device can remove partially cured and/or fully cured resinpieces from an area in which subsequent layers of a part are formed. Inparticular, a moveable wiper arm that is constructed to have some degreeof flexibility can be positioned to apply a force to the container of anadditive fabrication device without experiencing the mechanicaldifficulties that can be encountered when a rigid wiper is configured tomove across a surface. For example, imperfections in the surface orwiper can cause mechanical restriction of the movement of the wiper, andin some extreme cases, could cause the wiper to stop entirely.

According to some embodiments, a moveable wiper may include two portionsconnected via a joint having rotational freedom. The wiper blade may beconfigured to contact a surface of a resin container so that, when thewiper is moved laterally across the surface of the container, the wiperblade contacts the surface. The joint may allow one of the wiperportions (referred to as the wiper “blade”) to rotate away from thesurface of a container over which the wiper may be moved. In some cases,the other portion of the wiper (referred to as the wiper “arm”) isconfigured to not make contact with the container. The joint between thearm the blade may allow the blade to rest on the container surfacewhilst providing some force onto the surface. If motion of the wiperacross the surface of the container produces resistance against thewiper, the rotational joint allows the blade to move in a direction awayfrom the surface to allow the wiper to continue its motion substantiallyunimpeded.

According to some embodiments, the wiper arm and/or wiper blade maycomprise a flexible material to provide additional flexibility and/or toallow for additional vertical motion over and above that provided by therotational joint. The wiper arm and wiper blade may have differentmaterial compositions, or may have the same material composition. Insome cases, the wiper blade may be made from a more flexible materialthan the wiper arm.

The inventors have recognized and appreciated that an amount of forcenecessary to dislodge a partially or fully cured piece of resin from acontainer using a wiper will depend upon the area of the resin that isadhered to the container. For example, smaller resin pieces maygenerally be successfully removed using less force than would benecessary to remove larger resin pieces. As a result, by applying achosen force upon the wiper toward the container, embodiments may be“tuned” in the extent to which the wiper detaches comparatively smallerareas of residual material from the bottom of the container and theextent to which the wiper leaves comparatively larger areas of residualmaterial attached to the bottom of the container for removal by someother process and/or by manual intervention. The force can betransmitted to the wiper blade by configuring the shape and/or rigidityof the wiper arm, for example, such that the wiper blade is pushed ontothe container by the wiper arm with the desired force.

According to some embodiments, an additive fabrication device mayinclude a container having a portion shaped to catch pieces of resinmoved by a wiper arm. For example, a “trap” or otherwise recessedportion of a container may be positioned close to, or at, an edge of thecontainer and the wiper configured to move from the opposing end of thecontainer and over the recessed portion. Thus, the pieces of resin movedby the wiper may be moved into the recessed portion. The recessedportion may be a portion of the container in which additive fabricationdoes not take place. In this manner, the pieces of resin may beeliminated from affecting fabrication of subsequent layers by thedevice.

The inventors have further recognized and appreciated that selecting anamount of resin present in a container of an additive fabrication deviceclose to that of the fabricated layer height (e.g., 0.05 mm) may tend toreduce forces necessary to induce separation between an object beingfabricated and the bottom of a container. While liquid resin may besupplied to the container to maintain a resin depth close to that of thefabricated layer height, this may be insufficient to produce a uniformfluid level across the container. For instance, photopolymer resin canbe relatively viscous and may take a period of time to reach a steadyand uniform fluid level greater than is desirable for efficientfunctioning of an additive fabrication device. This time period maycause unwanted delays or, if not accounted for, failures or defectsduring object formation in subsequent steps. Furthermore, interactionsbetween the surface of the bottom of a container and the chemistry ofthe photopolymer resin may be such that photopolymer resin tends to beadon the bottom of the container, rather than spreading across it overtime. The inventors have recognized and appreciated that a wiper may beconfigured to overcome these difficulties and thereby aid in producing auniform thin layer of photopolymer resin within the container. Accordingto some embodiments, the wiper may perform this function while alsoproviding the above-described benefits with respect to removal ofpartially and/or fully cured resin adhered to the container or otherwiseremaining in the resin after formation of a layer of solid resin on apart.

According to some embodiments, a wiper may include a void space alsoreferred to herein as a “resin-retaining chamber.” In some use cases, avoid space may be provided within a wiper blade portion of the wiper.The chamber may be bounded at an upper surface (furthest from thecontainer and substantially parallel to the surface of the container)while including vents in one or both sides of the chamber orientedsubstantially perpendicular to the surface of the container. As thewiper moves through the resin, the resin moving through the vents may beoutput at a substantially uniform level in the container due tointeractions between fluid pressures within the void space.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, techniques for surface preparation foradditive fabrication. It should be appreciated that various aspectsdescribed herein may be implemented in any of numerous ways. Examples ofspecific implementations are provided herein for illustrative purposesonly. In addition, the various aspects described in the embodimentsbelow may be used alone or in any combination, and are not limited tothe combinations explicitly described herein.

FIGS. 2A-2B illustrate two views of an illustrative wiper, according tosome embodiments. In the example of FIGS. 2A-2B, system 200 isillustrated in which a wiper is positioned over the end of container 106and configured to slide across the base surface of the container (i.e.the surface on which the liquid resin rests) in the directions of thearrows shown in FIG. 2B. The wiper may, or may not, make contact withthe base surface. The wiper includes a support structure 206, a wiperblade 201 and a wiper arm 202. The wiper blade and wiper arm areconnected by a pivoting coupling 203.

According to some embodiments, the pivoting coupling 203 may be anysuitable mechanical connection having at least some rotational freedom.For instance, the coupling 203 may include a pin joint (also sometimescalled a “revolute joint” or a “hinge joint”), a ball and socket joint,a knuckle joint, or combinations thereof. According to some embodiments,the coupling 203 may permanently affix the wiper blade 201 to the wiperarm 202, and/or may attach to the wiper blade 201 in some other way,such as via a removable snap fit connection.

According to some embodiments, the wiper may be removably mounted ontothe container 106. Such a removable attachment may facilitate removing acontainer and installing the same or a different container. According tosome embodiments, the height of support structure 206 may be selected soas to push wiper blade 201 towards the bottom of the container.

According to some embodiments, the wiper blade 201 may be coupled to thewiper arm at a location along the axis of the wiper blade 201 orthogonalto the wiper motion direction shown in FIG. 2B. In such a configuration,a connection formed by the coupling 203 forms an axis of rotation alongthe length of the coupling 203 around which the wiper blade 201 mayrotate. That is, the wiper blade may include a portion that is locatedbelow the wiper arm in addition to a portion that extends beyond thewiper arm. For example, the coupling may be located approximately at amidpoint of the wiper arm along the axis of the blade orthogonal to thewiper motion, such that approximately half of the wiper blade is locatedbeneath the wiper arm (and therefore between the wiper arm and thecontainer). Such a configuration may allow the wiper blade to contactthe container whilst the wiper arm provides structural support but doesnot contact the container.

In addition to rotational flexibility, according to some embodiments thewiper arm 202 may comprise one or more flexible materials to provide foradditional vertical motion and flexibility or, as described above, tointroduce a force between the wiper blade 201 and the bottom of thecontainer by arranging the arm and blade components of the wiper toapply such a force once mounted to the side of the container.

According to some embodiments, wiper blade 201 may include at least onewiper edge that extends below the main body of the wiper blade 201substantially across the long axis of the wiper blade 201. Such an edgemay contact a container to move liquid photopolymer resin to desiredlocations.

FIGS. 3A-3B depict an illustrative stereolithographic printer thatincludes a wiper, according to some embodiments. Illustrativestereolithographic printer 300 comprises a support base 301, a displayand control panel 308, and a reservoir and dispensing system forphotopolymer resin 304. The support base 301 may contain variousmechanical, optical, electrical, and electronic components that may beoperable to fabricate objects using the system. During operation,photopolymer resin may be dispensed from the dispensing system 304 intocontainer 302. Build platform 305 may be positioned along the verticalaxis 303 such that the bottom facing layer of an object beingfabricated, or the bottom facing layer of build platform 305 itself, isa desired distance from the bottom 311 of container 302. The bottom 311of the container 302 may be advantageously transparent to actinicradiation generated by a source located within the support base (notshown) such that liquid photopolymer resin located between the bottom311 of container 302 and the bottom facing portion of build platform 305or an object being fabricated thereon, may be exposed to the radiation.Upon exposure to such actinic radiation, the liquid photopolymer may becured and attached to the bottom facing portion of build platform 305 orto an object being fabricated thereon. (FIGS. 3A-B represent aconfiguration of stereolithographic printer 301 prior to formation ofany layers of an object on build platform 305.) A wiper 306 isadditionally provided, capable of motion along the horizontal axis ofmotion 310 and which may be removably mounted onto the support base at309. The wiper may be coupled to one or more actuators (e.g., steppermotors, belts attached to motor(s), etc.) that produce lateral movementof the wiper across the surface of the container.

As discussed above, to successfully remove undesirable material withinan additive fabrication device, in some cases it may be desirable for awiper to move through a volume that might be occupied by an object beingfabricated by the device. Additionally, it may be desirable to move awiper in an additive fabrication device through photopolymer resin thatmay obstruct or inhibit motion of the wiper due to fluid forces.Embodiments of a wiper blade described herein may have one or more ofthese desirable characteristics and/or may exhibit other desirablecharacteristics. In some embodiments, a wiper blade may be mounted usinga rotationally flexible connection so as to provide a limited degree ofrotational freedom during operation. In some embodiments, the wiperblade may be configured with features that provide structural stability.

Illustrative wiper 306 shown in FIG. 3A is depicted in further detail inFIG. 4, according to some embodiments. In the example of the wiper 400of FIG. 4, the wiper blade 401 is mounted to a wiper arm 402 via a pin403. The pin 403 may permanently affix the wiper blade 401 to the wiperarm 402, and/or may attach to the wiper blade 401 in some other way,such as via a removable snap fit connection. As discussed above,according to some embodiments, a wiper blade 401 may be mounted at alocation offset approximately halfway down the axis of the wiper blade401 orthogonal to wiper motion 310. In such a configuration, aconnection formed by the pin 403 forms an axis of rotation along thelength of the pin 403 around which the wiper blade 401 may rotate, and aportion of the wiper blade (portion 409 in FIG. 4) is located beneaththe wiper arm.

According to some embodiments, the wiper arm 402 may include one or more“accommodating” features that limit the extent to which wiper arm 402interferes with the rotation of wiper blade 401 about the pin 403. Asshown in the example of FIG. 4, one such accommodating feature may be inthe form of a separation or gap within the wiper arm 402 so as to createa forked structure. In other embodiments, such accommodating featuresmay include portions of a wiper arm that are not within the desiredrange of motion of the wiper 401, such as above the wiper arm.

According to some embodiments, the wiper arm 402 may include a verticalfeature 406. Vertical feature 406 may provide clearance for the wiperarm 402 above the walls of a container (not pictured in FIG. 4), whilesubstantially reducing the amount of vertical clearance above the wiperblade 401 required during motion.

In some embodiments, rotational flexibility from pin 403 may be providedusing mounting devices such as a sufficiently flexible material in thewiper arm 402 and/or in the connection between the wiper arm 402 and thewiper blade 401. In addition to rotational flexibility, some embodimentsof the present invention may utilize a flexible material in the wiperarm 402 to provide for additional vertical motion and flexibility or, asdescribed below, to introduce a force between the wiper blade 401 andthe bottom of the container.

A cross section of wiper blade 401 shown in FIG. 4 is depicted in FIG.5. FIG. 5 depicts a cross sectional view 500 of wiper blade 401 alongthe horizontal axis of motion 310. Wiper blade 401 includes at a wiperedge 504 that extends below the main body of the wiper blade 401substantially across the long axis of the wiper blade 401 (e.g., indirections into and/or out of the page). Embodiments following theexample shown in FIG. 5 may utilize the wiper edge 504 to interact withthe bottom 311 of container 302, including moving liquid photopolymer orother materials to desired locations. In order to maximize theeffectiveness of such an operation, it may be desirable that the wiperedge 504 be maintained flush to the bottom 311 of the container 302during operation. As such, it may be particularly advantageous tocombine wiper edge 504 with an additional stabilizing feature, 501, inorder to improve the stability of the wiper blade 401, and thus wiperedge 504, during operation. In FIG. 5, the wiper blade is shown in crosssection, and in order to clearly depict void space 405, points at whichthe feature 501 attaches to the wiper blade are not shown.

In some embodiments, pin 403 mounting the wiper blade 401 to the wiperarm 402 may not provide sufficient constraint to the wiper blade 401 toprevent at least some undesired rotation around the long axis of thewiper blade 401. To mitigate this problem, the wiper edge feature 504and stabilizing feature 501, alone or in combination, provide additionalconstraints to the motion of the wiper blade 401 against the bottomsurface 311 of the container 302. In some embodiments, supportingfeature 501 may extend the full length of the wiper along the long axis.However, in some embodiments, supporting feature 501 may be present inonly particular sections of the wiper blade 401, such as being locatedat the middle and/or ends of the long axis of the wiper 401. Additionalsloping features 502 may be added to the wiper blade 401 in order toreduce the resistance of the wiper blade 401 when moving through theliquid material contained within the tank.

The configuration depicted in FIG. 5 may offer several advantages. As anexample, as mentioned above, it may be desirable that the wiper edge 504be maintained at a uniform distance from or flush to the bottom of thecontainer during operation. One way to maintain such a uniform distanceis to ensure the supporting structure constrains the motion of the wiperblade 401 in relation to the orientation of the container, particularlywith respect to the bottom of said container. Maintaining such anorientation (sometimes referred to as “tramming”) however, may be asource of operator and/or mechanical difficulty. In contrast, thelimited range of rotation allowed by mounting using pin 403significantly reduces the extent to which the wiper arm 402 and wiperblade 401 must be properly aligned with the bottom 311 and side surfacesof the resin container 302, while maintaining effective contact betweenthe wiper edge 504 and bottom 311 of the container 301. In addition, byaffixing the wiper blade 401 to the wiper arm 402 at a location towardsthe middle of the wiper blade 401, the wiper arm 402 forms acantilevered mount for the wiper blade 401 from only one side of thewiper 401, while still providing for sufficient support during theoperation of the wiper blade 401 in the additive fabrication processes.Such a mount may tend to allow for a more easily removable container401, as well as reducing the complexity of the mechanisms required tomount the wiper blade 401 onto the supporting structures.

As discussed above, it may be desirable for a wiper to incorporate avoid space, also referred to herein as a “resin-retaining chamber.” Asdiscussed above, a void space may be provided within wiper blade 201. Inthe example of FIG. 5, a chamber 405 is formed within the wiper blade401 with walls on four sides provided by the wall containing the wiperedge 504, the opposing wall with gap 505, and walls connecting theprevious two walls along the sides.

In the example of FIG. 4, the lower bound of the chamber 405 is leftopen so as to allow for the flow or resin into and out of the chamber405 through gap 505, as described in further detail below. The upperbound of the chamber 405 may be enclosed, but the wiper blade mayinclude one or more vents at locations above the expected resin level,so as to allow for pressure relief due to changing fluid levels withinthe chamber. In some embodiments, resin-retaining chamber 405 maycomprise substantially all of the interior volume of a wiper blade 401and extends across the long axis of the wiper blade 401 to cover thefull width of the object building area. In some embodiments,resin-retaining chamber 405 may be restricted with internal dividersand/or limits. In some embodiments, the inventors have found it may beadvantageous for the internal volume of the wiper blade 401 used as aresin-retaining chamber 405 to be between 5 cm³ and 25 cm³, such asbetween 10 cm³ and 20 cm³, such as approximately 13.8 cm³.

Illustrations of various stages of the operation of a wiper as describedabove in relation to FIGS. 2 and 4-5 are depicted in FIGS. 6A-6D,according to some embodiments.

In the example of FIG. 6A, a wiper blade 601 is illustrated in aninitial state prior to motion 600 across container 602. At this stage, alayer of photopolymer resin 613 covers the bottom of the container 602.This layer of liquid resin may be partially or fully depleted due toprior formation of one or more layers of an object being fabricated.

FIG. 6B illustrates a subsequent intermediate state after the wiperblade 601 has moved partially across the container 602 in a directionsuch that the wiper edge 604 trails the direction of motion 600. Themotion of the wiper blade 601 through the resin 603 causes at least aportion of the resin to flow through gap 605 up into the resin-retainingchamber 606. Due to the limited clearance between wiper edge 604 and thebottom of the container 602, only a limited portion of said resin withinthe resin-retaining chamber 606 may be capable of flowing out betweenthe bottom of the container 602 and the wiper edge 604. Accordingly, aportion of the resin flowing into the resin-retaining chamber 606through wiper edge 604 may tend to be retained by the chamber during themotion 600 of the wiper blade, while wiper edge 604 may leave a region614 of the bottom of the container 602 substantially clear of resinbehind the direction of motion. Accordingly, at the completion of themotion 600, as illustrated in FIG. 6C, resin may be contained within theresin-retaining chamber 606 and the bottom of container 602 in region614 may be substantially cleared of resin.

In the example of FIGS. 6A-6D, following the completion of the wipingmotion 600 in FIG. 6C the wiper may carry out a recoating step utilizingresin temporarily held within the resin-retaining chamber in order toenhance the recoating process. In said recoating step, shown partiallycompleted in FIG. 6D, the motion of wiper blade 601 may be reversed suchthat the gap 605 trails the direction of motion 610. With thetermination of motion 600, resin 610 is free to outflow from theresin-retaining chamber through the gap 605. By moving wiper blade 601along path 610, resin flowing out from the resin-retaining chamber maybe distributed across the bottom of the container 602 in a new layer ofresin 615. Embodiments providing for such deposition may advantageouslybe capable of establishing a substantially uniform layer of resin 615more quickly than may form without intervention, particularly inembodiments in which resin 615 is more viscous than water.

As discussed above, in some embodiments a wiper may be configured toremove partially cured material adhered to the bottom of a container. Insome cases, the wiper exerts pressure from a wiper edge against thebottom of the container.

To illustrate removal of residual cured or semi-cured materials, FIGS.7A-7B depict a wiper performing such removal. In the example of FIGS.7A-7B, wiper blade 701, and thus wiper edge 704, may be moved across thebottom of the container 702 in direction 700, as shown in FIG. 7A.During such motion, wiper blade 701 may exert a downwards force againstwiper edge 704 and/or the bottom of the container. A force applied viawiper edge 704 may be provided in various ways, such as by use of aflexible wiper arm (e.g., wiper arm 202 and/or wiper arm 402) placedunder tension.

According to some embodiments, the height of a structure (e.g., supportstructure 206) on which a wiper blade 701 is mounted may be selected soas to push wiper blade 701 towards the bottom of the container. Suchmounting may cause force to be exerted against the bottom of thecontainer by the wiper edge 704 (in addition to a stabilizing featuresuch as feature 501, should the wiper arm include such a feature).

According to some embodiments, the wiper blade 701 may be flexiblymounted onto a wiper arm to allow for pressure to be applied to thesurface of the container while maintaining alignment between the path ofthe wiper blade 701 and the bottom of the container 702. In someimplementations, an amount of pressure applied may be determined basedat least in part on the height at which the support structure mounts towiper blade 701. Once wiper edge 704 reaches the residual material 710,forces are applied to the residual material 710 by the wiper edge 704,potentially dislodging it from the container.

As will be appreciated by those having skill in the art, the extent towhich an area of residual material 710 is attached to the bottom of thecontainer, and thus the amount of force needed to dislodge it, may tendto increase as the area of the residual material 710 increases. In somecases, a downwards force exerted via wiper edge 704 may be insufficientto remove residual material 710. In such cases, the flexible nature ofthe mounting of wiper blade 701, as discussed above, may allow wiperblade 701 to pass over the residual material 710. In other cases, theforce applied may be sufficient to break the adhesive attachment betweenresidual material 710 and the bottom of the container. As a result, byapplying a chosen downwards force via wiper edge 704, embodiments of theinvention may be “tuned” in the extent to which small areas of residualmaterial 710 are detached from the bottom of the container and theextent to which larger areas of residual material 710 are left attachedto the bottom of the container for removal by some other process ormanual intervention. As may be appreciated, the amount of force to beapplied may depend upon additional factors, such as the nature of thebottom of the container and the geometry of the wiper edge 704.According to some embodiments, the inventors have determined that aforce between 4-6 Newtons, as measured at the central pivot point of thewiper blade 701 and the bottom of the container, may provide for optimalremoval of residual material 710. The inventors have further found thatthe use of such force may be most advantageously applied through a wiperedge 704 having a rounded profile, such as wiper edge 504 shown in FIG.5.

In some embodiments, freed residual material 711 may be left tocirculate within the resin 713 within the container, to be collectedlater, if needed, by some other process. The inventors have observedthat such free-floating cured material may cause substantially fewerdifficulties in later operations than residual material 710 adhered tothe bottom of the container. In some embodiments, as shown in FIG. 7B,freed residual material 711 may also be temporarily contained within theresin-retaining chamber 706 of the wiper blade 701. This material may bemoved to the edge of the container and left there during subsequentfabrication.

Alternatively, as shown in FIG. 8, freed residual material 812 may berelocated by the motion 800 of wiper blade 801 to a recessed region 815of the container not used for the exposure of photopolymer resin toactinic radiation. Said recessed region 815 may, in some embodiments, beat a lower position than the level of the remainder of the container inorder to help prevent freed residual material 812 from leaving thelocation 815.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art.

Such alterations, modifications, and improvements are intended to bepart of this disclosure, and are intended to be within the spirit andscope of the invention. Further, though advantages of the presentinvention are indicated, it should be appreciated that not everyembodiment of the technology described herein will include everydescribed advantage. Some embodiments may not implement any featuresdescribed as advantageous herein and in some instances one or more ofthe described features may be implemented to achieve furtherembodiments. Accordingly, the foregoing description and drawings are byway of example only.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Further, some actions are described as taken by a “user.” It should beappreciated that a “user” need not be a single individual, and that insome embodiments, actions attributable to a “user” may be performed by ateam of individuals and/or an individual in combination withcomputer-assisted tools or other mechanisms.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. An additive fabrication device configured to formlayers of material on a build platform, each layer of material beingformed so as to contact a container in addition to the build platformand/or a previously formed layer of material, the additive fabricationdevice comprising: a wiper, the wiper comprising: a wiper arm having alength and a first end, the length of the wiper arm extending in a firstdirection and being longer than a width of the first end; a wiper bladehaving a length and a second end, the length of the wiper bladeextending in the first direction and being longer than a width of thesecond end, the second end of the wiper blade being flexibly mountedonto the first end of the wiper arm, and the wiper blade comprising achamber bound at least in part by first and second sides of the wiperblade and an upper surface of the wiper blade; and at least onestabilizing feature configured to contact the container and constrainmotion of the wiper blade against the container when the wiper movesover the container.
 2. The additive fabrication device of claim 1,wherein the wiper blade comprises at least one opening in the uppersurface through which liquid may flow from the container into thechamber, and/or from the chamber into the container.
 3. The additivefabrication device of claim 1, further comprising the container, andwherein the at least one stabilizing feature causes the wiper blade tomaintain a fixed distance above the container when the wiper moves overthe container.
 4. The additive fabrication device of claim 3, whereinthe at least one stabilizing feature is attached to a lower surface ofthe wiper blade.
 5. The additive fabrication device of claim 1, whereinthe wiper blade is formed from a more flexible material than the wiperarm.
 6. The additive fabrication device of claim 1, wherein the chamberof the wiper blade has a volume between 5 cm³ and 25 cm³.
 7. Theadditive fabrication device of claim 1, wherein the wiper blade includesone or more vents within the first side and/or the second side of thechamber.
 8. The additive fabrication device of claim 7, wherein theadditive fabrication device is configured to maintain a level of aphotopolymer liquid within the container at a first height, wherein thewiper is configured to move across the container while making contactwith the container, and wherein the one or more vents of the wiper bladeare arranged wholly above the first height.
 9. The additive fabricationdevice of claim 1, wherein the chamber of the wiper blade comprises oneor more internal dividers.
 10. The additive fabrication device of claim1, wherein the at least one stabilizing feature is arranged at a firstend of the wiper blade.
 11. A wiper configured to be used within anadditive fabrication device comprising a container, the wipercomprising: a support structure configured to be attached to one or morecomponents of the additive fabrication device; a wiper arm flexiblymounted onto the support structure, the wiper arm having a long axisaligned in a first direction and having a first end; a wiper bladehaving a long axis aligned in the first direction and having a secondend flexibly coupled to the first end of said wiper arm, and comprisinga chamber bound at least in part by first and second sides of the wiperblade and an upper surface of the wiper blade; and at least onestabilizing feature configured to contact the container and constrainmotion of the wiper blade against the container when the wiper movesover the container.
 12. The wiper of claim 11, wherein the wiper bladecomprises at least one opening in the upper surface through which liquidmay flow from the container into the chamber, and/or from the chamberinto the container.
 13. The wiper of claim 11, wherein the at least onestabilizing feature is attached to a lower surface of the wiper blade.14. The wiper of claim 11, wherein the wiper blade is formed from a moreflexible material than the wiper arm.
 15. The wiper of claim 11, whereinthe chamber of the wiper blade has a volume between 5 cm³ and 25 cm³.16. The wiper of claim 11, wherein the wiper blade includes one or morevents within the first side and/or the second side of the chamber. 17.The wiper of claim 11, wherein the chamber of the wiper blade comprisesone or more internal dividers.
 18. The wiper of claim 11, wherein thewiper arm is flexibly mounted onto said support structure at a secondend of the wiper arm, and wherein the at least one stabilizing featureis arranged at a first end of the wiper blade.